Thanks for your replies guys.
I suppose in a way it was quite an ambiguous question and i should be brave enough to put out what lies beneath it.
I'm considering exploring other relationships myself. I'm not going hugely out of my way but like Ari and partner, if one should come my way I think I would now be open to it. This is more likely for us now because we have started meeting the local poly community.
What worries me is that it might upset my equilibrium. Things are really good for us right now and while part of that is due to my decision to participate in the lifestyle I am also a bit worried that it could upset our whole apple cart.
I know in the past I haven't been good with NRE so I'm very aware of the effect that could have. Bottom line I suppose is the question"how do you keep new relationships in perspective and not upset the wonderful relationship you already have? There I think that is actually what I would like to know.